Organic electroluminescent (hereinafter referred to as “organic EL”) devices make use of a charge transport thin film composed of an organic compound as a light emission layer or charge injection layer. Especially, a hole injection layer has a role of charge transport between an anode and a hole transport layer or light emission layer and plays an important function so as to achieve the low-voltage drive and high luminance of organic EL devices.
The formation of a hole injection layer is broadly classified into a dry process, typical of which is a vacuum deposition process, and a wet process, typical of which is a spin coating process. When comparing these processes with each other, a thin film having a large area and a high flatness can be formed more efficiently in the wet process. Therefore, a hole injection layer capable of being formed by the wet process has been demanded under the present situation where the formation of large-area organic EL displays is being in progress.
Under such circumstances, the inventors have developed charge transport materials that are applicable to a variety of wet processes and can be formed into a thin film capable of realizing excellent EL characteristics when applied to a hole injection layer of an organic EL device, and also compounds that are soluble in organic solvents used for the charge transport material and are useful as a charge transport material or dopant (e.g. see Patent Documents 1 to 7).